ENH Add Pyodide support

[hoodmane]

What do these changes do?

Adds support for Pyodide. Intended for discussion. Probably not an implementation we'd want to merge. It seems to be good enough for several downstream projects I've tested out.

I will try to get some simple CI working on this branch soon.

Related issue number

#7253

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
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• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
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    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[Dreamsorcerer]

Do you think we could encapsulate that logic into a custom Connector in some way, so _request() can work with minimal changes?

[hoodmane]

I think so. At the very least we'll need _request to check if it's Emscripten and probably wrap the Connection object into a PyodideConnection and use a PyodideRequest, but I think if we add:

if sys.platform == "emscripten":
   connector = PyodideConnector(connector)
   request_class = PyodideRequestClass(request_class)

in ClientSession.__init__ and provide appropriate implementations of PyodideConnector and PyodideRequestClass then it will work.

[Dreamsorcerer]

Yes, I think specifically, connector defaults to None. So, we can adjust the code to use the new connector on this platform or TCPConnector otherwise. So far, looks reasonable if you'd like to continue with this and complete the feature.

[psymbio]

Currently, for this issue, I compiled a wheel for multidict v4.7.6 (needs to be v5.0.0 <= and v4.5.0); and I try to install it inside jupyterlite and get the following issue:

Code for recreation:

import micropip
await micropip.install('https://raw.githubusercontent.com/psymbio/tiktoken_rust_wasm/main/packages/multidict/multidict-4.7.6-py3-none-any.whl', keep_going=True)
await micropip.install("aiohttp", verbose=True)
import aiohttp

Error:

```python

AttributeError                            Traceback (most recent call last)
Cell In[2], line 1
----> 1 import aiohttp

File /lib/python3.11/site-packages/aiohttp/__init__.py:6
      3 from typing import Tuple  # noqa
      5 from . import hdrs as hdrs
----> 6 from .client import BaseConnector as BaseConnector
      7 from .client import ClientConnectionError as ClientConnectionError
      8 from .client import (
      9     ClientConnectorCertificateError as ClientConnectorCertificateError,
     10 )

File /lib/python3.11/site-packages/aiohttp/client.py:32
     29 from multidict import CIMultiDict, MultiDict, MultiDictProxy, istr
     30 from yarl import URL
---> 32 from . import hdrs, http, payload
     33 from .abc import AbstractCookieJar
     34 from .client_exceptions import ClientConnectionError as ClientConnectionError

File /lib/python3.11/site-packages/aiohttp/http.py:7
      5 from . import __version__
      6 from .http_exceptions import HttpProcessingError as HttpProcessingError
----> 7 from .http_parser import HeadersParser as HeadersParser
      8 from .http_parser import HttpParser as HttpParser
      9 from .http_parser import HttpRequestParser as HttpRequestParser

File /lib/python3.11/site-packages/aiohttp/http_parser.py:15
     13 from . import hdrs
     14 from .base_protocol import BaseProtocol
---> 15 from .helpers import NO_EXTENSIONS, BaseTimerContext
     16 from .http_exceptions import (
     17     BadStatusLine,
     18     ContentEncodingError,
   (...)
     22     TransferEncodingError,
     23 )
     24 from .http_writer import HttpVersion, HttpVersion10

File /lib/python3.11/site-packages/aiohttp/helpers.py:100
     96 TOKEN = CHAR ^ CTL ^ SEPARATORS
     99 coroutines = asyncio.coroutines
--> 100 old_debug = coroutines._DEBUG  # type: ignore
    102 # prevent "coroutine noop was never awaited" warning.
    103 coroutines._DEBUG = False  # type: ignore

AttributeError: module 'asyncio.coroutines' has no attribute '_DEBUG'
```

aiohttp is trying to access asyncio.coroutines._DEBUG - which doesn't exist.

[Dreamsorcerer]

aiohttp is trying to access asyncio.coroutines._DEBUG - which doesn't exist.

Except, that's not our code. No idea what is happening with your traceback there, but that code doesn't exist in master, 3.8 or 3.9:
https://github.com/aio-libs/aiohttp/blob/3.8/aiohttp/helpers.py#L100

[psymbio]

Sorry, I forgot to mention the fact that this was done in JupyterLite, so according to this comment (pyodide/pyodide#4070 (comment)) the version installed was 3.6.2 (currently I'm not sure but after just glancing through the releases I can see v3.6.2 is probably the last release with a pure python wheel) so this issue exists there.

I think I'll try building a pure Python wheel for v3.8.6 and update the issue here.

Also, can building the pure Python wheel be added to the process?

[Dreamsorcerer]

Also, can building the pure Python wheel be added to the process?

If you create a PR, then probably. See #7632 too.
Although I don't really understand what a pure Python wheel offers that an sdist doesn't...

[hoodmane]

@Dreamsorcerer could you approve the CI to run? Ad hoc local tests run but I'd like to get a basic test running in CI.

[codecov]

Codecov Report

Attention: 59 lines in your changes are missing coverage. Please review.

Comparison is base (43f92fa) 97.36% compared to head (2607d49) 97.25%.

Files	Patch %	Lines
aiohttp/client_reqrep.py	20.00%	40 Missing ⚠️
aiohttp/connector.py	43.33%	17 Missing ⚠️
aiohttp/helpers.py	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7803      +/-   ##
==========================================
- Coverage   97.36%   97.25%   -0.11%     
==========================================
  Files         107      107              
  Lines       32346    32440      +94     
  Branches     3748     3758      +10     
==========================================
+ Hits        31494    31551      +57     
- Misses        647      688      +41     
+ Partials      205      201       -4     

Flag	Coverage Δ
CI-GHA	97.17% <39.79%> (-0.12%)	⬇️
OS-Linux	96.84% <39.79%> (-0.12%)	⬇️
OS-Windows	95.34% <35.86%> (-0.18%)	⬇️
OS-macOS	96.66% <39.79%> (+<0.01%)	⬆️
Py-3.10.11	95.26% <35.86%> (-0.18%)	⬇️
Py-3.10.13	96.65% <39.79%> (-0.18%)	⬇️
Py-3.11.6	96.36% <39.79%> (-0.18%)	⬇️
Py-3.12.0	96.46% <39.79%> (-0.15%)	⬇️
Py-3.8.10	95.23% <35.86%> (-0.18%)	⬇️
Py-3.8.18	96.59% <39.79%> (-0.18%)	⬇️
Py-3.9.13	95.23% <35.86%> (-0.18%)	⬇️
Py-3.9.18	96.62% <39.79%> (-0.18%)	⬇️
Py-pypy7.3.13	96.17% <39.79%> (?)
VM-macos	96.66% <39.79%> (+<0.01%)	⬆️
VM-ubuntu	96.84% <39.79%> (-0.12%)	⬇️
VM-windows	95.34% <35.86%> (-0.18%)	⬇️

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[hoodmane]

@Dreamsorcerer I guess the workflows need to be separately approved for each commit?

[hoodmane]

@Dreamsorcerer please trigger CI when you get a chance

[Dreamsorcerer]

I'm around most of tomorrow (and the next few hours) if you need me to keep approving.